The present invention relates generally to multiple chip modules (MCMs) that are utilized for radio frequency and intermediate frequency applications. More specifically, the present invention relates to MCM features that enable low-cost and high-volume manufacturing of modules that integrate the functionality of different active circuit chips.
Multiple chip modules (MCMs) are distinct electronic packages that may contain a number of bare and/or packaged integrated circuit (IC) chips and a number of discrete components (e.g., resistors, capacitors, and inductors) coupled to an interconnecting substrate. Traditional MCMs consist of a very complex multilayer interconnect substrate with several bare die and other components. Each prior art MCM has a custom size and need not necessarily fit a standard xe2x80x9cpackagexe2x80x9d format as commonly known in the IC packaging industry. In other words, each prior art MCM substrate (compared to an MCM package) is typically designed, handled, and tested in a different manner. MCMs are often utilized in a number of electronic applications, such as personal computers, mainframe computers, telecommunication, and telephony systems, where a number of components having similar electrical characteristics or having similar electrical paths can be grouped together in a single package. Although basic MCM design and manufacturing technologies are relatively well known, such conventional technologies have not facilitated a low-cost, high-volume production process. Many MCM packaging technologies house only bare die and some house bare die and discrete components. However, prior art MCM packages with bare and packaged dies and discrete components are utilized for multi-GHz applications. In addition, conventional MCM techniques have not been extended to radio frequency (RF) applications, e.g., applications having circuits operating at frequencies greater than approximately 800 MHz, and intermediate frequency (IF) applications, e.g., applications having circuits operating at frequencies between approximately 200 and 800 MHz.
The increasing demand for higher levels of circuit integration, lower manufacturing cost, easier upgradeability, and smaller component sizes has been very difficult to meet in the context of RF and IF applications. This difficulty is related to a number of practical reasons. For example, shielding and signal isolation between different RF and/or IF circuit components typically limits the number of active components that can be included in a single MCM. In addition, regulatory limits on electromagnetic interference (EMI) and emissions may further restrict the design parameters associated with conventional RF/IF modules. Furthermore, thermal dissipation from some RF circuit chips may place another burden on conventional module designs.
As a result of the foregoing shortcomings of prior art designs, conventional RF/IF packages are generally limited in terms of use in high-volume applications. At best, conventional RF/IF MCMs function at a component level (below the subsystem level); a number of physically discrete MCMs are typically used to achieve an operable subsystem or system in conjunction with a motherboard that serves as an interconnect structure. Each of the individual MCMs may be adequately shielded to avoid RF interference with one another and to reduce the amount of EMI emissions associated therewith. Unfortunately, the use of individual MCMs increases the design and manufacturing cost because individual partitioning, matching, and isolation networks may be required between the various MCMs.
In addition to the above problems, conventional MCMs may not be sufficiently flexible to accommodate a number of design alternatives. For example, it may not be possible or economical to combine surface mount and wire bonding techniques in a single prior art MCM and it may not be possible to include different active IC types (e.g., CMOS, GaAs, bipolar) on one prior art MCM substrate. Furthermore, conventional MCMs may not have the flexibility to utilize different types of vias for thermal sinking and RF grounding purposes or the flexibility to employ different types of terminations from application to application.
In accordance with the present invention, a single RF/IF MCM may include a plurality of active circuit chips and a plurality of discrete components coupled to one interconnecting substrate. The MCM can be configured to perform any number of different RF/IF functions such that it operates as an independent subsystem. A high level of integration, the use of RF isolation techniques, and the use of thermal sinking techniques enable the MCM to function in a manner equivalent to a number of separate conventional modules without the associated design and manufacturing costs. In addition, an RF/IF MCM may be designed in a flexible manner that contemplates various manufacturing, electrical, environmental, and testing parameters.
The above and other advantages of the present invention may be carried out in one form by an MCM having an interconnect substrate, a number of surface mount passive components coupled to the interconnect substrate, and at least one active circuit device coupled to the interconnect substrate. The at least one active circuit device is configured to perform a plurality of RF functions such that the MCM operates as an integral package.